Mobile electrical devices such as cellular phones often employ rechargeable batteries which, due to weight and size constraints, require frequent recharging. While many battery charger designs exist, all available designs fail to meet at least one of the many challenges facing the designer of the fully integrated battery charger and power supply for world-wide mobile use.
A first challenge arises from the multi-level power demands of some electrical devices. For example, available cellular phone and notebook computer batteries require a certain power input to be charged, while the phones or computers themselves require another input level to be powered directly. This problem is accentuated for the user who wishes to utilize a mobile electronic device in a truly mobile environment such as a car or boat, which normally supplies only de power and often subjects the device to extreme vibration for extended periods of time. While various adaptors and conversion circuits are available which can make most small electrical devices run in a truly mobile environment, such add-on devices can quickly become burdensome for the traveler who wishes to minimize the effect of the vibration in the mobile environment and the baggage associated with achieving true electronic mobility.
A second design challenge arises from the desire of many users to continue using their electrical device while charging a battery which may or may not be connected to the device. This challenge was addressed with some success by Weiss, et al., as disclosed in U.S. Pat. No. 5,059,885, assigned to Motorola, Inc. and incorporated by reference herein in its entirety. Weiss is directed to a battery charger housing including a battery positioning and support apparatus. However, available commercial embodiments of the apparatus disclosed in Weiss require an external power supply to power an internal battery charging circuit, thereby adding to the complexity and burden of using the available apparatus. Moreover, while the apparatus disclosed in Weiss can accommodate batteries of varying sizes, gravity is the only means disclosed in Weiss for maintaining the batteries in a charging position. Thus, the apparatus disclosed in Weiss may prove less than optimal in a truly mobile environment, such as a boat or car, wherein the charger may not remain level throughout an unsupervised charging session. Finally, the user of the Weiss apparatus must detach a charging battery or electrical device attached thereto from the charger housing to use the battery or device.
One available and very popular battery charger and power supply for cellular telephones, marketed by Motorola, Inc., incorporates a dual use stand similar to the stand disclosed by Weiss, wherein a phone and battery can be placed and separately charged and powered. However, this design remains dependent upon an external power supply, requires the user to detach the electronic device to make use of it, and fails to address the security requirements necessary for a design compatible with the truly mobile environment.
Another challenge in charger design arises from the fact that while many electrical devices are sold for use throughout the world, there is no world standard for electrical plug configurations, size, shape, position or number of prongs. The wide variety of socket configurations in use worldwide burdens international suppliers of mobile products to varied countries and international travelers who wish to use electrical devices in a portable fashion.
Most industrial nations use a standardized alternating current supply with a hot side and a neutral side. Some plugs specifically incorporate a separate earth or ground lead while others do not. A problem exists, therefore, with physically accessing an AC current source supplied through any number of outlet configurations and interfacing that current source with the appropriate input connections for the power supply and/or battery charger as well as with the device to be powered and/or the battery to be charged.
The traditional solution for the mechanical prong configuration problem is to provide an adapter which includes a socket to accommodate the prongs of the electrical device integrated with a second set of prongs in a configuration for a local socket. These adapters suffer from some significant problems. The most significant problem is that the adapters are bulky and at a minimum cause the prongs of the original device to be extended by at least the length of the additional set of prongs. Since most plug devices are designed to be secured by spring tension and interaction with a wall plug, this can pose a significant mechanical disadvantage. The increased lever arm created by the additional prong length will tend to shift the plug downward, tending to pry the plug out of the wall socket. This will be true even for a light weight plug.
The lever arm problem is accentuated with devices that are larger than a simple plug. Many battery chargers and power supplies are designed to be wall-mounted at a wall socket. A typical device includes a casing which terminates in a plug designed to plug directly into the wall socket. The casing is often designed to lie against a wall to provide mechanical stability and to maintain the plug prongs in proper contact with the wall socket. If an adapter must be used, the unit loses the stability of resting against the wall and, because even a small amount of weight at the end of a lever arm will create a torque which will tend to pry the prongs out of the wall socket, such a plug adapter is generally unusable for such wall-mounted plug-in devices. Also, sometimes plugs are situated on a wall or surface in such a manner that the device cannot be adequately secured near the wall, in which case a flexible unit which can be used in either a wall mount or a surface-top configuration is required.
Angling the plug severely can compromise the electrical connection to the point that the plug no longer is in electrical contact with source current. This type of angling may lead to partial separation from the wall socket and may expose the prongs of the plug in such a way that a person or animal might come into contact with live current, thereby causing bodily harm.
A further problem with existing plugs is the awkward shape of the plug with prongs protruding from the end. If, for example, a plug is moved from location to location, the prongs of the plug extend outward and can be difficult to pack or store or can catch on clothing when packed into a travel case.
A few plug devices have been designed with a plug or prongs which fold into a casing. For example, some rechargeable flashlights include the collapsible prongs which can be rotated into a position extending out from the body of the flashlight and plugged directly into a wall socket or extension cord. In another example, some telephone charging stations include a cradle for the telephone and a rotatable plug which can be extended into position for plugging into a wall socket, or collapsed into a space in the shell of the charging station, particularly so that a user may slip a charging station into a pocket, a briefcase, or other container.
Presently available collapsible plug devices suffer from various problems which make them inconvenient or even dangerous to use. In particular, the rotatable plug has only a weak spring holding the plug in position. It does not take much effort to collapse the plug, which may cause the plug to partially or completely pull out of a wall socket. This can compromise the electrical connection to the point that the plug no longer is in electrical contact with source current. In some circumstances, this may expose the prongs of the plug in such a way that a person, might come into contact with live current, thereby causing bodily harm. In addition, a collapsing plug might pinch the user.
Accordingly, for the mobile user there is a need for a charging device which can be-flexibly incorporated into a variety of work environments, which can supply charging power from a variety of AC and DC electricity sources in known international configurations, which can charge batteries without monopolizing use of the battery-powered device benefitting from the charge, which enables the user to continue using the device while the device receives power from the charger, and which can directly power the device, all in an easy to use and compact package.